1. Field of the Invention
The present invention relates to an oil seal of a hydraulic shock absorber.
2. Description of the Related Art
In a hydraulic shock absorber for a vehicle, as described in Japanese Utility Model Application Laid-Open No. 5-3739, an oil seal is sealed in an opening portion of a cylinder, and a first lip and a second lip of the oil seal are slidably contact with a piston rod at two axial positions in a side of an oil chamber of the cylinder and a side of an outer portion thereof.
In a damping property of the hydraulic shock absorber, various kinds of frictions or the like are added to a hydraulic damping force generated by a damping force generating valve, whereby a total property is indicated.
According to the conventional hydraulic shock absorber, an unstable riding feeling such as a waft feeling is given on a flat road surface, in particular, when the hydraulic damping force is low, so that it is not so preferable.
An object of the present invention is to improve a riding feeling of a vehicle in a hydraulic shock absorber by paying attention to a shape of an oil seal and a material.
The present invention relates to an oil seal of a hydraulic shock absorber provided with a first lip and a second lip which are sealed in an opening portion of a cylinder and are slidably in contact with a piston rod at two axial positions in a side of an oil chamber and a side of an outer portion of the cylinder, wherein
the oil seal is made of a nitrile rubber of a low nitrile, and wherein
an inner diameter of the second lip is set to be smaller within a range between 0.3 and 1.0 mm xcfx86 than an outer diameter of the piston rod.